have 2000 blazer 4.3, driving along the batt. light illuminates, truck dies imediatly cranks with no restart,fuel pump operating. try restart a couple days later fires up and runs few minutes. batt. light illuminates,dies. no restart since, but as you start to turn key the batt. light comes on imediatly. cranks easily,can hear fuel pump and smell fuel. I will check for fuel pressure as soon as gauge arrives

 

In my experience, when the "battery light" comes on on the dash when you are driving, it means it is your Alternator!!!